You Notice That a Device with a Manual IP Address

You notice that a device with a manual IP address cannot communicate with other devices on the network. The network has the address 192.168.4.x with a subnet mask of 255.255.255.0. The IP address of the non-communicative station is 192.168.3.12/24. What is the most likely reason this system cannot communicate?

A) It has the wrong subnet mask
B) It is using a private IP address
C) Its IP address is on a different network
D) The TCP/IP stack is corrupt